Ultrasonic transducers are known that may be employed in parametric speaker systems for generating sonic or ultrasonic signals in nonlinear transmission media. For example, an array of ultrasonic transducers may be employed in a parametric speaker system for generating sonic (i.e., audio) signals in air or water. A conventional parametric audio system typically includes a modulator configured to modulate an ultrasonic carrier signal with at least one audio signal, at least one driver amplifier configured to amplify the modulated carrier signal, and an ultrasonic transducer array comprising a plurality of ultrasonic transducers configured to direct the modulated and amplified carrier signal through the air along a selected path of projection. For example, the ultrasonic transducer array may comprise a plurality of self-contained electrostatic transducers, piezoelectric transducers, electrostrictive transducers, electro-thermo-mechanical film (ETMF) transducers, or polyvinylidene fluoride (PVDF) film transducers. Because of the nonlinear transmission characteristics of the air, the projected ultrasonic signal is demodulated as it passes through the air, thereby regenerating the audio signal along at least a portion of the selected projection path.
In the conventional parametric audio system, the level of audible sound produced by the system is generally proportional to the total surface area of the ultrasonic transducer array, and the coverage area of the sound generated by the array. However, this can be problematic because a typical ultrasonic transducer, such as the typical piezoelectric transducer, has a diameter of only about ¼ inch. As a result, it is often necessary to include hundreds or even one thousand or more piezoelectric or electrostatic transducers in the ultrasonic transducer array to achieve an optimal transducer array surface area.
Although the ultrasonic transducer might be made larger to achieve higher levels of audible sound, this can also be problematic. For example, an electrostatic transducer typically includes a backplate member that is supported by a vibrator film. However, as the electrostatic transducer increases in size, the size of the backplate also increases, thereby potentially damaging the thin vibrator film supporting the larger backplate. Moreover, each of these small transducers is individually connected within the ultrasonic transducer array and typically configured to be stand-alone operable, which can significantly increase both the complexity and the cost of manufacture of the parametric audio system.
It would therefore be desirable to have an improved ultrasonic transducer that can be employed in a parametric speaker system. Such an ultrasonic transducer would provide a highly reliable and reduced cost solution to implementing an ultrasonic transducer array within the parametric speaker system.